A motor-pump unit of this type is disclosed in DE 199 27 658 A1. In general, a motor vehicle brake system is filled with the necessary pressure fluid after the assembly of the individual system components such as in particular a master brake cylinder, a tube and hose line system, the motor-pump unit and wheel brakes at the vehicle manufacturer's premises. For this purpose, the entire brake system is evacuated in a first process step, while the pressure fluid provided is introduced in a second process step.
It has shown that roller bearing assemblies of motor-pump units are exposed to high stress, which is untypical of roller bearings, in particular during the pressure fluid filling process. Due to an alternate application with vacuum or excess pressure, respectively, it may e.g. occur in sealed roller bearings that sealing elements such as sealing lips are detached. This fact, in turn, can cause lubricants to be washed out and, consequently, can lead to a reduced lifetime of the pump. The bearings will fail prematurely what is problematic in particular in brake systems with long pump operating times as is the case in electrohydraulic brake systems in particular. Bearings, which are not sealed, provide a free access to the roller surfaces and do not allow using a special lubricant. This entails problems when the lubricating properties of the pressure fluid used are not appropriate, or when the pressure fluid contains wear particles that can cause damage to the running surfaces.